Means for automatic weight control in well drilling



Feb. 24,` 1942. w. A. Looms l l2,274,339.

MEANS `-FOR AUTOMATICl WEIGHT CONTROL `IN WELL DRILLING Arron/veis Feb. 24, l942. y w. A. LooMls 2,274,339

MEANS FOR` AUTOMATIC WEIGHT CONTROL. IN WELL DRILLING Filed Jan. '5, 1959 s sheets-sheet 2 W /NVENToR BY WAL TER A. OGM/5' ATTORNEY.

j Feb. 24, 194.2. y l w. A, Looms 25274339 MEANS FOR AUTOMATIC WEIGHT CONTROL IN WELL DRILLING Filed Jan. 5,1939 s sheets-smeet s ln s ATTORNEY Patented Feb. 24, 1942 MEANS FOR AUTOMATIC WEIGHT CONTROL IN WELL DRILLING walter a Loomis, Whittier', Calif.

Application January 5, 1939, 'Serial No. 249,398

(ci. ass-19) 2 claims.

. This invention relates to oil well drilling equipment and particularly pertains to a meansfor automatic weight control in well drilling.

In the drilling of wells, and particularly oil V wells, great difficulty is experienced in drilling a well in a manner to produce astraight well bore. This is due to the fact that the formation being penetrated varies in character both as to matejrial and as to hardness, and furthermore, for the reason that some formations are disposed at an inclination to the horizontal plane being penetrated with the result that at different depths the drilled hole may deviate from the vertical. 'I'hese conditions are aggravated when the drill is notv fed into or through formations at a speed appropriate to their physical character and hard-l iisl ness, as for example when a hard stratum is encountered land the drilling speed is not retarded, the drill will produce a condition known as overfeeding which will cause the drill to tend to drill in a plane at right angles to the angle of inweight control the pressure responsive means acted upon by variation of the weight has been applied to the live end of the drill supporting cable and attempts have been made to initiate and interrupt the feeding movement in response to tension variation in the live end of the cable. a i

It has been found that the friction set up in the traveling block tends to reduce the tension in the live end of the cable over the actual value of tension created by` the weight imposed upon the cable. This produces an over-sensitive condition when the tension responsive means is placed on the live end of the 'cable and thus acts to render the device unsatisfactory in its operation.- When the tension responsive means is placed on the dead end of the cable the friction of the travelingV block tends to increase the tension on the dead end of the cable sothat all of the friction of the traveling block is thrown to the dead end of the traveling block. For .that reason it isl desirable I to apply the tension responsive means to the dead clination of thehard stratum, and in thus being.

defiected will deviate the Well bore from the 1 vertical. Attempts have been made to apprise the driller of the condition of the geological formation being encountered by the drill so that he could vary the feed of drilling appropriately. Such operations haveusually involved the use of a weight indicator which measures the tension on the drill cable, and thus indicates the proportion of the weight of the drill-string which is imposed upon the drilling cable and the correspending proportion of weight resting' on the formation being drilled. This requires that the driller constantly watch the weight indicator and attempt to adjust the feed appropriately as more or less weight is indicated as being imposed upon the supporting cable. This often necessitates a relatively slow driving speed of the rotarytable in order to lcautiously proceed.' It sometimes happens that such a method of procedure with manual regulation is inaccurate so that at times the drill will be over-feeding andi at other times it will be under-feeding when it could be advancing rapidly into the formation. When over-fed deviation of the drill bit takes place; when underfed the bit will drill of bottom and spin. With some types of bits excessive wear will then occur both on the bit itself and'in the roller bearings. Under certain circumstances of drilling lit becomes necessary to retract the drill and drill y while attempting to come out of the hole. The

' tension imposed upon the drilling cable is im.

portant under such circumstances.

In most instances of attempted automatic to end of the cable since the action will be less violent due to the damping effectof the friction in the traveling block. It has, however, been found to be necessary to set the tension responsive means so that the drill will be at all times feeding downwardly so that under no circumstances the drill feed will be interrupted entirely since this insures a more accurate feed operation and prevents subsequent inoperation after .thefeed ofthe drill string-has once been stopped.

It is the principal object of the present invention, therefore, to provide a weight control for drill rigs which is -fitted with means whereby-accuratemanual operation and adjustment of drilling equipment may be made, and whereby after a desired adjustment and setting of the drill feed is effected the apparatus will act automatically to maintain a continuous drill feed with direct reference to the degree of resistance of the for'- matlon being penetrated to the cutting action of the drill bit. l

The present invention contemplates the pro' vision of an automatic weight control for o il well drilling rigs which may be used in connection with any type of rotary drilling apparatus now in use and which when set will feed the, drillstring downwardly to act to maintain this feed constantly downwardly while appropriately varying the feeding speed with direct reference to the character of .the formation being penetrated, the structure including adjusting means to determine and set the normal rate of feed either downwardly or upwardly and automatic means for controlling the rate of feed and tending to restore the feed from variation to the predetermined set speed.

'I'he invention is illustrated by way of example in the .accompanying drawings, in which:

Figure 1 is a view in side elevation illustrating a commercial type of oil well drill rig and dis,-

Vclosing the application of the present invention thereto.

Fig. 2 is a view in diagram showing the general layout of the apparatus.

Fig.. 3 is an enlarged'view in vertical section showing the automatic weight control unit.

Fig. 4 isan enlarged view of the fluid responsive means applied to the drilling cable.

Fig. 5 is an enlarged view in plan as seen on the line 5-5 of Fig. 3 and discloses the construction of the control lever arrangement.

Referring more particularly to the drawings,

I0 indicates a derrick used in oil wellY drilling. This derrick has the usual fioor with relation to which it is suitably anchored and upon which v a power unit I2 is mounted. This power unit may be of any desired type, such for example as those commonly used in connection with drawl works drives either employing electric, steam or a worm gear I8 driven by the speed varying transmission I3. One end of a 'drilling cable I8' is mounted to pass around the windingdrum I4. The drilling cable I8 is led upwardly and over the sheaves I9 of a crown block 28 and after being led around the traveling block 2| the dead end of the cable is properly anchored, as indicated at 22 in Fig. 1 of the drawings. Connected to the traveling block 2| is 'the swivel 24 carrying the upper end of a kelly bar 25 andto which bar the usual' drill string 28 is attached. Mounted at the lower end of the drill-string 28 is a drill bit 21 which operates in a well bore 28. The wellvbore 28 penetrates the geological formation of the earth and it is the prime object of this invention to control the feed of the drill 21. -in ,and through the formation at appropriate speeds with relation to the character of the forvmation being penetrated.

'mounted upon the cable and generally indicated at 80 in the drawings. This structure is of the general type oi device known as a Martin-Decker weight indicator, shown particularly in Fig. 4 oi the drawings.

The weight indicator includes a bowl ll across which a diaphragm 32 is disposed and is held by a cover plate 38. A suitable pressure plate l 34 rests against the diaphragm to deilect the same and has associated with it a post 35 carrying a saddle 38 across which the cable I8 lies. 'This post has a threaded mounting 31 with relation to the pressure plate for purposes of adiustment, as will be hereinafter set forth. A guide for the post is indicated at I8. Carried upon the body hooks over the cable I8 at one side of the saddle.

88, and carried at the diametrically opposite side of the body member '30 is'an adjustable hook structure 40 which operates on the border of a C clamp and may be tightened or loosened by an adjusting screw 4|. Connected with the bowl 3| is a pressure tube 42 which leads to the automatic weight control unit 43.

Referring more particularly to Fig. 3 -of the drawings, it will be seen that the automatic weight control unit comprises an outer housing 44 within which a pressure responsive device 45 is positioned. This device is in communication ing plate48 to' which a sylphon bellows 41 is s mounted. The bellows 41 extend vertically and downwardly from the plate 48 and rest within a cup 48. The cup 48 is formed with an annular lip 49 around its upper outer edge to provide a seat for an expansion spring 58 which rests upon a plate 5|. The plate 5| is secured with relation to the top plate 46 and the top wall of the housing 43 by a plurality ofbolt hangers 52. The lower end of the cup 48 is formedswith a central boss 53 which extends downwardly and is threaded'to receive the threaded end 54 of a thrust rod 55. This rod extends through a tubular adjusting nut 58 which is mounted through a threaded opening in the plate 5| and stands in the path of the lower face of the boss 53 so as to limit downward movement of the cup and also limit downward movement of the thrust rod 55. The thrust rod 55 is formed in two pieces which are longitudinally aligned and threaded at their contiguous ends so that they may be coupled together by a nut 51 and may be adjusted as desired. The lower section of the rod is indicated at 55' and it is shown as terminating in a needle valve 58 which extends into a valve seat 59 formed in a plunger 80. The plunger 80 reciprocates within a dash pot cylinder 8| by which violent movement of the thrust rod 55 is resisted. Theneedle valve is threaded through a boss 82 formed on the top of the dash pot and controls the flow of an incompressible iiuid from above the plunger 60 through ports 83 and the valve `seat 58 to the space within the dash pot and below the plunger, and vice versa. A nut 84 isf provided to lock the needle valve 58 in its set position While a cap 88 is detachably mounted over the dash pot to close and protect the same.

The dash pot structure acts to damp out vibrations from the pump and also vibrations occasioned by rough digging. It is necessary to properly adjust the thrust rod for a particular operation and for that purpose an indicating nger 88 is adjustably secured on to the thrust rod 55. This indicating ringer has a horizontally extending portion 81 which assumes an indicating relation with regard to xed ngers 88 and 88 n carried by a plate 10 and rigidly secured to the mediate its ends which is carried by an auxiliary member is a relatively xed st irrup $9 which 75 lever 11. 'Ihe auxiliary lever 11 is pivoted at the opposite end from the pin 18 upon a pivot pin The upper around which it may oscillate in a vertical plane. Carried beneath' the free end of the vauxiliary `lever 11 is a pair oi magnets 19 mounted on the wall of the housing 44. V'I'he magnets are spaced from each other and disposed upon' the opposite sides of the longitudinal center o1 the lever 11, while an armature plate 80 is carried upon the lever 11. The free end of the lever is fitted with an arcuate gear segment 8| which is in mesh with a gear pinion 82 mounted upon a pivot 93 carried by the auxiliary lever 11. Extending downwardly from and rigidly secured with relation to the pivot p in 83 is a contact arm 84.. v'I'his arm will oscillate in a plane parallel to that of the levers 15 and 11 under circumstances to be hereinafter pointed out.

The lever arm 15 is acted upon by a tension spring 85 to tend to move the gear segment 8| upwardly since the weight -of the leverl arm lconnection |26. A conductor |21 leads 'from would normally cause it to swing downwardly.

The spring also takes lost motion out of the linkage. The contact arm extends downwardly to swing over the vertical face of amounting plate 86 which carries adjustable contacts 81 and 88. These contacts are disposed upon'oppo- -site sides of the arm and may engage contact elements 89 and 90 carried by a spring iinger `9| mounted upon the arm 94. An adjusting screw 92 limits movement of the spring finger in one direction, and a spring 93 limits movement of the contact arm in its opposite direction. An adjusting vscrew 94 vis provided to vary the tension of the spring 93 for purposes to be hereinafter described. Attached to the free end of the contact arm 84 and on the same side thereof as occupied bythe spring 93 is a' hair spring 95 which tends to hold the contact arm in proper eduilbrium since it is necessary -to accurately balance the spring finger 9| and its contacts. be-

tween the contacts 01 and 8 8 carried by the mounting block 86.

vided to establish electrical communication between the wire |'|4 and the wire H6. The conductor ||5 is connected with a lead wire ||1. 'Ihis leads to pole y| I8 of a relay ||9. A circuit is-completed from the conductor H6 through a relay switch |20, here shown as a double break single pole switch, the opposite pole |2| of which connects with a conductor |22. This wire leads to a coil |23 of a down solenoid |24'. A conductor |25 leads from the coil |23 to a ground said ground connection to coil |28 of up solenoid |29. This has aconductor |30 which connectswith switch |3| of relay switch |32. Other details of the solenoids |24 and |29 will be ex plained hereinafter.

struction and embodies the use of two coils and a single plunger. The plunger is indicated at |33 and is connected to an extension member |34. The plunger slides through a bushing |35 around which the coils |23 and |28 are wound. Mounted lbetween the two coils isa collar |36 and at the ends' thereof are collars |31, upon which are mounted an outer metal sleeve |38. The plunger Y |33 1s of a length shorterthan the length of the bushing |35 and stands midway the length of this bushing under normal conditions. A bumper disc |39 of resilient material is secured at the outer end of the structure and against which the vplunger |33 may strike. Stop lugs |40 mounted withina cage |42 are engaged by a stop washer 243 mounted upon the plunger lextension |34 beneath the shoulder 244 and limit opposite move-l ment of the plunger.

The mock as is adjustabiy mounted at' as' to an operating rod |00. 'This rod is horizontally sudabie through a bearing lol and through the side wall of the housing`44. Mounted at the outer end of the rod |00 is a roller |02 which bears against a cam |03 carried upon a piston rod |04.

'I'his piston rod |04 is connected with the tilting block 4structure |3 by which speed variation andl direction of `transmission of power is controlled in a transmission of the hydraullc'type. The piston rod extends into a hydraulic operating cylinder |05 `and is connected with a piston |09 reciprocating therein. 'I'he opposite ends of thel operating cylinder |05 are tted with fluid conduits |01 and |09 which lead to the oppositeends of a pilot valve cylinder |09. The pilot valve' cylinder |09 is ntted with a piston'l |0 carrying a piston rodllll. An oil well pressure lin'e ||2 leads into the pilot valve cylinder. The pilot valve cylinder, by which speed and direction of the draw-works transmission are controlled, isv operated indirectly through .the control structure generally indicated as being enclosed in housing 43 and shown in Fig.. 3 of the drawings.

pole of 'which is connected witha ground wire ||3 and the opposite pole of which is connected with a power lead wire ||4. A switch I5 is pro- Inv addition to the control structure shown in The washer 243 is held in its uppermost position by a spring 245 and it is limited in its upper movement by stop lugs 245 carried by the cage |42." y

By this arrangement it will be seen that the plunger |33 may move in either direction a limited distance as influenced by the coil of a par# ticular solenoid. It is to be understood that the extension member |34 is made of non-magnetic `material so that when either of the solenoid coils is. energized there will be a tendency for the plungerr to move toward that particular end of the solenoid to close the gap normally occurring in the magnetic eld. The plunger extension |34 is connected to the piston rod of the pilot valve ||0.

The relays H9 and |32 are intended to control thesolenoids |24 and |29 by manual action and by automatic action. The control of the relays for manual action includes an up switch |43 and a down switch |44. vided with a conductor |45 which leads to binding post |45'ofrthe relay. A conductor |41 leads from the binding post to the coil of relay- |32'. A conductor '|48 leads from this binding post to contact post |49 of automatic relay |50. The

down switch |44 is provided with a conductor |5| which leads to binding post |52 of relay II9..

A conductorr|53 leads from this binding post tothe coil of relay ||9 while another conductor |54 'connects with the binding post |52 and leads to contact post |55 of an automatic control relay |58.' The opposite sides ofthe relay magnets construction and func? The switch |43 is prorelay |50. The connection |64 leads from the binding post |63 to a contact |65 carried by an armature |66 of the relay |50 and is adapted to engage the contact post '|49 of that relay. The end of conductor |6I is secured to binding post |61 to which a conductor |68 is connected. This conductor is secured to a contact |66 carried by the armature of the relay |56. Thus, when -electrical contact is made between the contact post |40 and |65 a ground circuit will be completed to the ground connection |60 from con-- ductor |46, and when electrical contact is made between contact post |55 and |60 a ground circuit is completed from the ground connection |60 to the wire |54. It will thus be seen that the conductor |50 provides a common ground connection for both the up and down switches |43 and |44, and that a separate ground connection is provided for the two relays ||9 and |32 as controlled by the relays |50 and |56.

The magnets of the relays |50 and |56 are energized when an automatic control switch |`l| is closed. This switch is provided with a con-4 of these coils are provided with ground connes-- tions ill and |15. rihe distributing wire it@ connects to one side of the magnet coil of relay HitV by a wire |19. A wire i8@ connects to the opposite side of the coil of the relay |55. lThis wire is secured to la binding post im. A conductor |82 leads from the binding post to con I tact 88 of the automatic control switch, as shown in Fig. 3 of the drawings. I

The relay |50 connectsl with wire Hd through conductors |53 and |043. @ce wire ifl connects to one side of the magnet or relay |56.;

A wire |95 connects to the opposite side of the magnet and to a binding post |66. The wire t3@ leads from the binding post |66 to a conductor |09 connected to a condenser |60.

agresse By reference to Fig. 3 of the drawings attention is directed to the fact that the rodv |04 of the operating piston Anot only carries the. cam |03 but a double faced cam |58 over whichla roller |90 may move. ,This roller is mounted upon a connecting link 200leading to the throttle of-the engine or other prime mover. This acts to accelerate the engine speedas thecontrol apparatus advances the feed..A By this means'it is insured that the engine will not stall under increased loads. s

In operation of the present invention the endrilling cable I6 is, however, somewhat diiierent due to the fact that the control apparatus including its switch operates inresponse to a substantially constant pressure intermediate the extreme pressures regardless of the weightimposed upon the drilling cable i8 by the drillstring suspended thereon. It is, therefore, necessary to vary the' amount of deflection of the cable |8 occurring between the members 39 and i0 and the intermediate saddle 36. This is done by adjusting the saddle on its threaded mounting and by appropriate adjustment of the screw ti attached to the clampv d0. When light loads are imposed upon the drilling cable iii such as when drilling at the top of the hole the saddle 36 is moved outwardly and the clamp id is drawn inwardly. This produces a relatively great deiiection in the portion of the drilling cable i@ occurringbetween the hook 59 and the clamp du. It will berecognized that correspondingly a greater pressure will be imposed upon the diaphragm i3 and the iiuid within the bowl.

it@ vthan would have otherwise been the case. When, however, the depth of the drilled hole has materially increased the saddle 35 is adjusted so that the member 31 is shorten-ed and at the same time the clamp lil with its threaded member iii are loosened. This will produce less deliection in the portion of drilling cable occurring between members s6 and 4|@ and will restore the effective duid pressure within the bowl 3| to substantially The binding post |8| of the relay |56 is provided with a conductor 96| which leads to one side of a condenser |52. The condensers have acommon lead wire |03 attached by a wire |64 to a suitable resistance |55. The opposite side of the resistance is provided with a ground connection |96. The wire |85 also connects with s.

- wire |01 which leads to contact member 81 of` the control mechanism shown in Fig. 3 of the drawings. v

The contact finger 0| carried by the arm 6d is, as has been previously' described, provided with contacts 00 and 00 which may be moved into electrical engagement with the contacts 81 and-v the same pressure as when a lesser amount of pipe was suspended ori the drilling cable |23 so that a pressure gauge 20| would be maintained at practically the same indication all the time, and the pressure upon the fluid within the conduit 42 would be substantially constant. This fluid pressure is transmitted from the unit 30 through the conduit 42 to the sulphon 41 within the automatic control unit 43. The result will be that the pressure will distend the sulphon 41 against the tension of the spring 50 and will tend to force the thrust rod downwardly. This will act against the member 55' and the plunger to displace the fluid within .the dash pot 6| through the valve seat 59 and the ports 63 as controlled by the adjustment of the needle valve 56. The limit of downward movement of the sulphon and its cup 48 is set by adjustment of the threaded bushing 56. It is intended, however, that the sulphonand the thrust rod 55 may have a desired movement above this limit, and that the movement of the pressure rod may be upwardly as well as downwardly. The intermediate position of the pressure rod at the mean pressure of the fluid within the line 42 is intended to maintain the indicator finger 61 at a point midway between the members 63 and 69.

When the apparatus is thus adjusted it is desired to set it with relation to the pressure created by a particular amount of weight imposed upon the drilling cable I and with the remaining weight resting upon the formation being penetrated. As drilling proceeds it is to be understood that the apparatus is so set as `to insure that a continuous substantially constant drilling feed is maintained, although this feed varies in either direction from a mean feed rate as produced bydrilling conditions. As the structure reaches a position of excessive hydrostatic fluid pressure -in the' pipe 42, the fluid may be bled and the clamp must be readjusted. It has also been found that when large temperaturev unit may then be set to operate at a determined rate of speed, after which the clutch may be lthrown in on the draw-worksl by letting the suspended load down upon' the formation with theline shaft clutchout. The clutch on the machine may then be put into'engagement by letting the load further down.` When this clutch supports the load the brake commonly present on the draw-works is released. Care should be taken to never tie the brake down with the -the transmission jis`in proper gear. .The powerolf from the bowl 3| of the pressure responsive 1` means -30 to restore the pressure to the normally yset pressure for feeding. lWhen, however, excessive pressures are reached then the saddle 36 ing conditions.

' must be set to feed the drill'string downwardly clutch in engagement. A constant feed is now .taking place on the `-drurn I4 to pay out the cable lI3 at aepredetermined constant rate of speed. The lswitch |44, which is the down man.-

ual control switch is then closed, so that the.

adjustment so that the drill will dig Aat an emcient rate of speed.y It is to be understood 4that in setting theimechanism to drill at a desired rate of speed opening and closing of the down switch |44 and the up switch |43 may be brought about manually to effect operation of the relays H9 or |32, and thus appropriately actuate solenoids |24 and |29,'whereby"the pilot valve structure |09 will be moved to control operation of the operating cylinder |05 and the piston therein. In the event, however, that automatic operation is-required the switch |1| is closed after onpivot 16 and its segment 3| .acts with the pinion 33 to swing arm v34. At thesame time the relays and |56 and the relays ||9 and |32 will be properly connected so that they may operate the respective relays controlling the ap.

propriate down solenoid |24 or'the up solenoid |29 as relay circuits are completed from the contact finger 9| carried by the arm 34 and as the contacts 39 and 90 carried by this finger move into or out of electrical contact with the contact members 31 and 03, respectively. It is understood that these conditions of contact may be brought about by movement of the thrust rod acting through the arm 1| and the 4link 12 to the lever 15, or by movement of'the member |00 as shifted by the cam |03 on the piston rod |04 of the operating piston |06. Thus, feeding speed and drilling weight are correlated to produce automatic regulation of the apparatus and to maintain the apparatus undereillcient drill- It may be also necessary to adjust the spring 93 and also the hair spring to a particular set of conditions.

In further analysis of the structure here disclosed it will be evident that since theautomatic feed mechanism is at all times acting to maintainA a constant feed of the drill string although at varying rates and that the cable tension creating this variation is damped due to the friction ofthe traveling block, the automatic control constantly' at pressures varying from a set minimum. Thus, asl tension-increases, due t6 the penetration of a less resistant cutting material, the thrust rod 59 moves downwardly in turn swinging the lever 15l to swing upwardly in the -direction of the arrow a in Fig. 3 of the drawings, and will at the same time act through the gear elements 3| andj32 to swing the contact arm 34 in the direction of the arrow b. This will produce contact between the members 9| and 33 completing the circuit, which would'cause i the downward feed of the drill to be accelerated. As this takes place the piston rod |04 moves upwardly and carries the cam |03 with it to relieve pressure on the roller |02 of the operating rod |00. The spring |00' will then act to movethe rod |00 outwardly so that the roller the pilot valve has been-set by manipulation of Y the solenoids |24 and |23. Prior to the closing of this switch it will -be understood that the mayl oscillate freely on` its auxiliary lever 11 y pivot 'I3 since themagnets 19 are not energized.

|02 will follow` and maintain contact with the inclined face of the cam |03. This will bodily move the mounting block 36 until contact is broken between the'members 9| and 33, at which time 1t will be recognized that the tension of the deadend of the cable and the pressure produced throughthe tension responsive means 30 will have reached the predetermined tension for the' minimum rate of feed of vthe drill string, after which drilling operations will continue with the lever 15 set at 4its new angle and the piston |06 set at its new control speed. At the same time the mounting block 36 will be disposed at a new position and the spring 93 will be out of contact with the lever 04. If still lighter cutting material isv encountered the lever 15 will When, howeverythe automatic switch |1| is.

n closed the electric circuits through the magnets 19 .will be energized to lock the arm `11 in rigid I relation to the housing. The lever 15 then swirigs.v

swing upwardly .farther and the lever 34 and the mounting block 66 willy move farther to the left. with reference to Fig.-3. When, however,

dead end of the cable I3 will be decreased and the fluid pressure in theSylphon bellows 4-1 tact with the member 31 a-readjustment of tl formation is encountered which would cause over-feeding at the set speed, the tension on the by the position of the cam |03, will be restoredv and contact between the members 9| and 8l broken. YWhen, however, this readjustment has taken place until an exceedingly low rate of speed of downward feed is producedthe lever 84 will again encounter the spring 93, which will tend to resistfurther swinging movement of the lever 84 counter to that indicated by the arrow 'b. This will act to prevent the feed mechanism from completely interrupting downward feed of thel drill.

Attention is also directed to the fact that by the use of the automatic mechanism indicated in Figs. 2 and 3 and the magnetic setting of the levers 'l5 with relation to lever 11 themagnet acts as a clutch to cause the automatic control to dominate and maintain substantially the same condition in the apparatus as existed at the moment automatic control is initiated. IThis makes it possible for the automatic control strucf ture, including the levers l5 and ll and the maga net la, to he utilized ln various settings other than those indicated in the drawings.

When all of the adjustments on the apparatus have been properly made the machine will act automatically with a negligible amount of error in either direction rom the adjusted position. l't will also be recognized that since the feed is constant the drill pipe never stops moving in the selected direction so that the structure becomes much more sensitive than would be the case when feeding is interrupted by hand adjustment. rihis makes it possible for drilling operations to be carried on at a relatively high rate of speed.

'It will thus be seen that the structure here disclosed comprises a simple operatlngmechanism having a convenient manual control operable at a remote point iromvthe apparatus and a convenient automatic control which includes the manipulation of only one control switch or loutton. it will be seen that by this arrangement a desired rate of speed may be manually controlled in either direction, after which the structure may be instantly set to maintain a speed o feed selected. When a desired speed of feed has been selected the automatic control may be thrown in yes so that the machine will continue to feed at substantially the selected speed although varying appropriately to maintain the necessary weight which was resting on the bottom of the hole at made, after which the drilling will continue in a manner to insure the drilling of a straight hole 'at a maximum cutting speed and lby automatic means.

While I have shown the preferred form ofv my apparatus and method of operating the same, it will. be understood that various changes may be made in the combination; construction and arrangement of parts by those skilled in the art, without departing from the spirit of my invention as claimed.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. A rotary well drilling apparatus comprising a rotary table, a drill string fed downwardly therethrough and driven thereby, a drill bit at the lower end of said string, means for supporting the drill string whereby a determined proportion of the weight of the drill string may be permitted to rest upon the formation being penetrated, feed means associated with the drill string support. means connected therewith to feed the drill string downwardly continuously at a rate of speed above a set minimum, speed varying means associated with said feed means and responsive to variation in the amount of weight of the drill string being supported by the formation being penetrated and whereby the rate of speed may be accelerated or decelerated above the set minimum speed until a predetermined proportion of weight is supported by the formation, a power unit for driving said feed means, and means automatically accelerating the speed of vsaid power unit when a `feed adjustment is made by the apparatus.

2. A control device of the character described including a prima mover and a responsive member, constantly linked intermediate levers between said prime mover and responsive member for translating movement from the prime mover to the responsive member, said intermediate levers being normally ineective in translating movement, and optionally controlled means for rendering said intermediate means effective in translating movement, said optionally controlled means including a member adapted to act mag# netically in holding parts of the intermediate means rigid with relation to each other.

WALTERA. LOOMIS. 

